It is now possible to discriminate between cancers caused by intake of a radioactive material and those that arise spontaneously Recently, scientists from the Helmholtz Zentrum Munchen have identified a genetic change in thyroid cancer as a signature or fingerprint that points to a previous exposure of the thyroid to ionizing radiation. They discovered the gene marker in papillary thyroid cancer cases from the victims of Chernobyl; this marker was absent in the thyroid cancers in patients with no history of radiation exposure. This breakthrough has profound biological significance. Now, for the first time, scientists have been able to discriminate between the cancers caused by the intake of a radioactive material and those that arise spontaneously. Cancer occurence Most cancers occur spontaneously or when cells get exposed to certain viruses or chemicals or a physical agent such as ionizing radiation. So far, there was no way to identify uniquely a radiation cancer from a naturally occurring cancer. The researchers led by Prof Horast Zitzelsberger and Dr Kristian Unger from the Radiation Genetics Unit of the Helmholtz Zentrums Munchen in collaboration with Prof. Geraldine Thomas, Imperial College London, examined the thyroid cancers from children exposed to the radioiodine fallout from the accident at the Chernobyl nuclear power station. After decay For comparison, they looked for the same genetic change in thyroid cancers of children born more than one year after the explosion, after all radioiodine decayed away. Iodine-131 has a half life of 8 days. Scientists found that the number of copies of a small fragment of chromosome 7 was increased only in the cancers from the irradiated children. Writing in the May 23, 2011 issue of the Proceedings of the National Academy of Sciences(PNAS), the researchers noted that this is one of the first genetic markers that indicate a radiation aetiology of cancer. Normally, humans have 46 chromosomes. Two copies of chromosome 7, one inherited from each parent are present in every cell. Forty one disorders are associated with genes on chromosome 7. Changes in the number or structure of chromosome 7 occur frequently in human cancers. According to National Institutes of Health (NIH), some genes in chromosome 7 may play critical roles in controlling the growth and division of cells.